CN107408796A - Manufacturing method of spark plug - Google Patents

Abstract

The invention provides a technique for suppressing a decrease in accuracy of a spark discharge gap of a spark plug. A method of manufacturing a spark plug, the spark plug comprising: a center electrode extending in an axial direction; a main body metal case provided on the outer periphery of the center electrode; and a ground electrode having a rod shape, wherein a base end of the ground electrode is joined to the metal shell, and a tip end of the ground electrode is bent toward the axial line side, wherein the method includes a bending step of bending the unbent ground electrode by pressing the unbent ground electrode, which is the unbent ground electrode, against a predetermined curved surface of a bent pad, the bent pad being configured to be separable into two or more members including a 1 st member having a mounting portion for mounting the bent pad to a fixing jig, and a 2 nd member having a predetermined curved surface for contacting the unbent ground electrode.

Description

Manufacturing method of spark plug

technical field

The invention relates to a spark plug.

Background technique

Conventionally, a spark plug is used for ignition of an internal combustion engine such as a gasoline engine. In the spark plug, a spark gap (spark gap) is formed between the center electrode and the ground electrode by bending the ground electrode toward the axis of the center electrode so that the top end surface of the ground electrode faces the center electrode. In a state where the ground electrode is joined to the main metal case, the ground electrode is bent toward the center electrode using a bending spacer (for example, refer to Patent Document 1).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2005-243260

Contents of the invention

The problem to be solved by the invention

In the method of manufacturing the spark plug described in Patent Document 1, in the bending process of the ground electrode using the bending spacer, a load accompanying the bending of the ground electrode is applied to the bending spacer. Deterioration of the portion in contact with the ground electrode may reduce the accuracy of the spark discharge gap of the spark plug. Therefore, an object of the present invention is to provide a technique for suppressing a decrease in accuracy of a spark discharge gap of a spark plug.

solutions to problems

The present invention is made to solve the above-mentioned problems, and the present invention can be realized by the following technical means.

(1) According to a technical solution of the present invention, there is provided a manufacturing method of a spark plug, the spark plug includes: a center electrode extending along the axis direction; a main body metal shell, which is arranged on the outer periphery of the center electrode; and a ground electrode , which is rod-shaped, the base end of the ground electrode is joined to the main metal shell, and the top end of the ground electrode is bent toward the axis side. This spark plug manufacturing method includes a bending step of bending the unbent ground electrode by pressing the unbent ground electrode, that is, the unbent ground electrode, against a predetermined curved surface of the bending spacer. The curved spacer is configured to be divisible into two or more members including a first member and a second member, the first member has a mounting portion for mounting the curved spacer on a fixing jig, and the second 2. The member has the predetermined curved surface for contacting the unbent ground electrode. In the method of manufacturing the spark plug according to this aspect, since the bending load for bending the unbent ground electrode acts on the bending spacer, there is a possibility that the mounting portion or the predetermined curved surface may be damaged due to the stress accompanying the bending load. breakage. Since the bending pad is configured to be divisible into two or more members including the first member and the second member, when the bending pad is damaged, only the member including the damaged part is replaced to stabilize Furthermore, the spark discharge gap of the spark plug is formed with high precision. In addition, since only the member including the damaged part can be replaced, the replacement cost of the jig can be reduced. As a result, according to the manufacturing method of the spark plug, the manufacturing cost of the spark plug can be reduced.

(2) In the spark plug manufacturing method according to the above-mentioned aspect, among the two or more members constituting the curved spacer, at least two of the members may have a convex portion. And the other member has a recess capable of fitting into the protrusion. By doing so, when replacing one of the member having the concave portion and the member having the corresponding convex portion, the two members can be easily combined appropriately by fitting the concave portion and the convex portion. Therefore, according to the manufacturing method of the spark plug, when the bent spacer is damaged, the member can be replaced in a short time, so the increase of the manufacturing time of the spark plug can be suppressed, and the reduction of the production efficiency can be suppressed.

(3) In the spark plug manufacturing method according to the above-mentioned technical means, in the curved spacer, the toughness of the first member may be higher than the toughness of the second member, and the hardness of the second member may be higher. on the hardness of the first member. By doing so, it is possible to suppress the occurrence of damage to the first member and the generation of damage to the second member in a balanced manner.

(4) According to the spark plug manufacturing method of the above technical solution, the ground electrode of the spark plug may also include an electrode tip, and the electrode tip is bonded to the top end and is configured to connect the electrode tip with the The center electrodes are opposed to the center electrodes with a predetermined gap between them, and the curved spacer has grooves capable of accommodating the electrode tips on the predetermined curved surface for contacting the unbent ground electrode part, the groove part includes a first side surface, a bottom surface and a second side surface, the first side surface is arranged on the top end side of the second member of the curved spacer, the bottom surface is continuous with the first side surface, the The second side is opposite to the first side and continuous with the bottom, the first side and the bottom are connected with a rounded corner with a radius of R1, the second side and the bottom are connected. The bottom surfaces are connected by a rounded corner with a radius R2, and the radius R1<the radius R2. The portion of the bent spacer in which the groove portion is formed tends to be cracked at the site where stress is concentrated. In this spark plug manufacturing method, the fillet radius R2 of the connection portion between the second side surface and the bottom surface to which a large stress is applied is made larger than that between the first side surface and the bottom surface in the groove portion of the curved spacer. The fillet radius R1 of the connection part can suppress the stress concentration, thereby suppressing the damage of the bending pad. As a result, it is possible to suppress the cost and time required to replace the bent spacer member in the manufacturing process of the spark plug, and to suppress an increase in the manufacturing cost of the spark plug and a decrease in production efficiency.

(5) In the method for manufacturing a spark plug according to the above-mentioned means, if any of the members of the bending spacer is damaged, the method for manufacturing the spark plug may include: A step of replacing the damaged member. According to this method, when the bending spacer is damaged, only the damaged member is replaced, thereby reducing the replacement cost of the jig.

The present invention can be realized in various technical solutions, for example, the present invention can be realized in technical solutions such as a spark plug manufacturing device, a spark plug, and a sensor.

Description of drawings

FIG. 1 is an explanatory diagram showing a partial cross section of a spark plug.

Fig. 2 is a process diagram illustrating a method of manufacturing the spark plug.

Fig. 3 is an explanatory diagram showing enlarged main parts of the prebending device.

Fig. 4 is an explanatory view for explaining the structure of the curved spacer.

Fig. 5 is a perspective view showing an appearance structure of a second member of the bending pad.

FIG. 6 is an explanatory view for explaining prebending.

Fig. 7 is an explanatory diagram for explaining the main bending process.

detailed description

A. The first embodiment

A－1. Structure of spark plug

FIG. 1 is an explanatory diagram showing a partial cross section of a spark plug 100 . In Fig. 1, the axis CA, which is the axis of the spark plug 100, is used as the dividing line. The appearance shape of the spark plug 100 is shown on the left side of the paper of the axis CA, and the cross section of the spark plug 100 is shown on the right side of the paper of the axis CA. shape. In the present embodiment, the part of the spark plug 100 located on the lower side of the paper in FIG. 1 is referred to as the “tip side”, and the part located on the upper side of the paper in FIG. 1 is referred to as the “rear end side”. In FIG. 1 , mutually orthogonal XYZ axes are illustrated. The Z-axis shown in FIG. 1 is an axis extending along the axis CA. Among the Z-axis directions (axis directions) extending along the Z-axis, the +Z-axis direction is a direction going from the rear end side toward the top end side of the spark plug 100 .

The spark plug 100 includes a center electrode 10 , an insulator 20 , a main metal shell 30 , and a ground electrode 40 . In this embodiment, the axis CA of the spark plug 100 is also the axis of the components of the center electrode 10 , the insulator 20 and the main metal shell 30 .

The spark plug 100 has a spark gap SG (spark gap) formed between the center electrode 10 and the ground electrode 40 on its tip side. The spark plug 100 is configured to be attachable to the internal combustion engine 90 in a state in which the tip side where the spark discharge gap SG is formed protrudes from the inner wall 91 of the combustion chamber 92 . When a high voltage (for example, 10,000 volts to 30,000 volts) is applied to center electrode 10 with spark plug 100 attached to internal combustion engine 90 , spark discharge occurs in spark discharge gap SG. The spark discharge generated in the spark discharge gap SG can ignite the air-fuel mixture in the combustion chamber 92 . The spark discharge gap SG in this embodiment corresponds to the gap specified in the claims.

The center electrode 10 of the spark plug 100 is a conductive electrode. The center electrode 10 has a rod shape extending in the direction of the axis CA. The outer surface of the center electrode 10 is electrically insulated from the outside by the insulator 20 . The tip side of the center electrode 10 protrudes from the tip side of the insulator 20 . The rear end side of the center electrode 10 is electrically connected to the terminal metal fitting 19 provided on the rear end side of the insulator 20 .

The insulator 20 of the spark plug 100 is an insulator having electrical insulation properties. The insulator 20 has a cylindrical shape extending around the axis CA. In this embodiment, the insulator 20 is produced by sintering an insulating ceramic material such as alumina. The insulator 20 has a shaft hole 29 which is a through hole extending in the direction of the axis CA. In the shaft hole 29 of the insulator 20 , the center electrode 10 is held on the axis CA in a state where the center electrode 10 protrudes from the front end side of the insulator 20 .

The main metal shell 30 of the spark plug 100 is a conductive metal body. The main metal case 30 has a cylindrical shape extending in the direction of the axis CA. In the present embodiment, the main metal case 30 is a member formed by nickel-plating cylindrical low-carbon steel. In other embodiments, the main metal shell 30 may be a member that has been galvanized or a member that has not been plated (no plating). The main metal shell 30 is fixed to the outer surface of the insulator 20 by crimping in a state of being electrically insulated from the center electrode 10 . An end surface 31 is formed on the front end side of the main metal shell 30 . The insulator 20 protrudes from the center of the end surface 31 in the +Z-axis direction (tip direction) together with the center electrode 10 . A ground electrode 40 is bonded to the end surface 31 .

The ground electrode 40 of the spark plug 100 is a conductive electrode. The ground electrode 40 has a rod shape, and one end (hereinafter also referred to as a base end) of the ground electrode 40 is joined to the end surface 31 of the main metal case 30 . The ground electrode 40 is bent toward the axis CA after extending in the +Z-axis direction from the end surface 31 of the main metal case 30 . In this embodiment, the ground electrode 40 has an electrode tip 45 at the tip. The electrode tip 45 is joined to the top end of the ground electrode 40 so as to protrude from the top end of the ground electrode 40 in the +Y-axis direction. The electrode tip 45 is arranged opposite to the center electrode 10, and a spark discharge is formed between the electrode tip 45 and the center electrode 10. Clearance SG. As shown in the figure, the position of the tip of the ground electrode 40 in the Y-axis direction is on the −Y-axis side relative to the center electrode 10 . That is, the length of the ground electrode 40 is shorter than when the position in the Y-axis direction of the tip of the ground electrode 40 is aligned with the center position of the center electrode 10 . As a result, the heating temperature of the ground electrode 40 can be kept low, and it is possible to suppress oxidation and breakage of the ground electrode 40 due to the heat received.

In the present embodiment, the material of the ground electrode 40 is a nickel alloy whose main component is nickel (Ni). In this embodiment, the material of the electrode tip 45 is an alloy containing platinum (Pt) as a main component and 20% by mass of rhodium (Rh). In other embodiments, as long as the material of the electrode tip 45 is a material with excellent wear resistance against spark discharge, it can be a pure noble metal (for example, iridium (Ir), platinum (Pt), rhodium (Rh), and Ruthenium (Ru), etc.), nickel (Ni), or other alloys containing at least one of these metals may be used.

FIG. 2 is a process diagram illustrating a method of manufacturing the spark plug in the present embodiment. The constituent parts of the spark plug 100 are fabricated in advance.

The center electrode 10 is inserted into the shaft hole 29 formed in the insulator 20 (step S10). Specifically, the center electrode 10 , ceramic resistors, seals, and terminal metal fittings 19 are inserted into the interior of the insulator 20 in a predetermined order, and these members are integrally formed by a heating and compression process called glass sealing.

Next, the unbent ground electrode 40 (hereinafter also referred to as unbend ground electrode 40A) is joined to the front end surface of the main metal case 30 before the insulator 20 is assembled by resistance welding (step S12 ).

The insulator 20 integrated with the center electrode 10 by glass sealing is inserted into the inner side of the main metal case 30, and the crimping portion of the main metal case 30 is bent to be bent inwardly, whereby the main body The metal case 30 and the center electrode 10 are assembled (step S14). Thereby, the insulator 20 is integrally held by the main metal case 30 in a state where the tip of the center electrode 10 protrudes from the front end side of the main metal case 30 .

The electrode tip 45 is joined to the inner side surface of the unbent ground electrode 40A joined to the main metal case 30 by resistance welding (step S16 ). A member in which the unbent ground electrode 40A is welded to the main metal case 30 in this way is also referred to as a workpiece.

Bending processing is performed on the unbent ground electrode 40A (step S18). The bending process (step S18) includes a preliminary bending process (step S182) of bending the unbent ground electrode 40A with a bending radius R (step S182) and a main bending process of forming a spark discharge gap SG between the center electrode 10 and the tip 45 (step S184). . In step S182 , pre-bending processing is performed using the pre-bending device 300 .

FIG. 3 is an explanatory diagram showing enlarged main parts of the prebending device 300 . The pre-bending device 300 has a bending block positioning mechanism part 310, a bending block 311, a bending mechanism part 330, and a bending roller (bending jig) 331 (FIG. 3). The bending pad positioning mechanism part 310 in this embodiment corresponds to the fixing jig in the claims.

A spacer 311 is installed in the curved spacer positioning mechanism part 310, and the top end surface of the center electrode 10 is aligned with the curved spacer 311 by moving the curved spacer 311 along the axial direction of the center electrode 10 (the Y-axis direction in FIG. 3 ). The distance between them is adjusted to a predetermined value, and the curved spacer 311 is positioned to create a predetermined gap between it and the top end surface of the center electrode 10 .

The bending mechanism part 330 drives the bending roller 331 so that the bending roller 331 presses the unbent ground electrode 40A toward the bending spacer 311 . As will be described in detail later, the curved spacer 311 has an abutment surface 319 against which the inner side surface 412 of the ground electrode 40 abuts. The roller 331 is driven by the bending mechanism part 330 in a state where the workpiece 150 in which the unbent ground electrode 40A is joined to the main metal case 30 is mounted on a workpiece holding part (not shown) and the spacer 311 is arranged at a predetermined position. And the unbent ground electrode 40A is pressed against the contact surface 319 of the curved spacer 311 .

FIG. 4 is an explanatory diagram for explaining the structure of the curved spacer 311 . FIG. 5 is a perspective view showing an appearance structure of a second member 311B of the bending spacer 311 . FIG. 6 is an explanatory view for explaining prebending.

As shown in FIG. 4 , the curved spacer 311 is formed by combining a first member 311A and a second member 311B, and fastening them with a screw 320 to join them together. The first member 311A is formed using alloy tool steel SKS3 (JIS G 4404:2006), and the second member 311B is formed using high-speed tool steel SKH54 (JIS G 4403:2006). The first member 311A has higher hardness and higher toughness than the second member 311B. On the other hand, the toughness of the second member 311B is lower than that of the first member 311A, but the second member 311B has higher hardness than the first member 311A. In the Rockwell hardness test (JIS Z 2245:2011) using the first member 311A and the second member 311B, the hardness of the first member 311A (made by SKS3) is less than HRC20, and the hardness of the second member 311B (made by SKH54) is HRC62～HRC66.

The first member 311A includes an engaging portion 314 , screw holes 315 , 316 , and 323 in which internal threads are formed, and two recessed portions 322A. The engaging part 314 and the threaded holes 315 and 316 are structures for installing the bending pad 311 on the bending pad positioning mechanism part 310 . By engaging the engaging part 314 of the first member 311A with the bending block positioning mechanism part 310 ( FIG. 3 ) and using the bolts 312 and 313 through the threaded holes 315 and 316 of the first member 311A, the bending block 311 is fastened to the The block positioning mechanism part 310 is bent, so that the curved block 311 is installed on the curved block positioning mechanism part 310 . On the other hand, the screw hole 323 and the two recesses 322A are structures for joining the first member 311A and the second member 311B.

As shown in FIG. 5 , the second member 311B has a substantially square truncated pyramid shape with curved side surfaces. The second member 311B includes a contact surface 319 (curved surface), a groove portion 317 , a concave portion 318 , a through hole 321 , and two convex portions 322B. The through hole 321 and the two protrusions 322B are structures for joining the first member 311A and the second member 311B. The two convex portions 322B of the second member 311B have a shape capable of fitting respectively with the two concave portions 322A of the first member 311A. As shown in FIG. 4 , by respectively fitting the two convex portions 322B of the second member 311B into the two concave portions 322A of the first member 311A, and screwing the screw 320 into the second member 311B through the through hole 321 The threaded hole 323 of the first member 311A is connected to the first member 311A and the second member 311B. In this embodiment, the spacer 311 is composed of two members, the first member 311A and the second member 311B, but since the first member 311A and the second member 311B are respectively provided with recesses 322A that can be fitted on the joint surface Therefore, for example, when the second member 311B is damaged and needs to be replaced, the first member can be easily arranged in an appropriate position as long as the concave part 322A and the convex part 322B are fitted together. The member 311A is joined to the second member 311B.

As shown in FIG. 6 , the abutting surface 319 of the second member 311B is a surface on which the inner side surface 412 of the ground electrode 40 abuts, and has a curved shape corresponding to the curved shape of the ground electrode 40 . The recessed portion 318 is a hollow in which the center electrode 10 is arranged during the prebending process. The contact surface 319 in this embodiment corresponds to the curved surface specified in the claims.

The groove portion 317 is formed on the abutting surface 319 so that the electrode tip 45 is not in contact with the bending spacer 311 when pre-bending the unbent ground electrode 40A, but is accommodated in the groove portion 317 . As shown in FIG. 5 , the groove portion 317 forms a substantially rectangular pyramid-shaped pit, including a bottom surface 317a, a first side surface 317b on the front end side of the curved spacer 311, a second side surface 317c opposite to the first side surface 317b, and a bottom surface 317a. The 3rd side 317d which connects the 1st side 317b and the 2nd side 317c. The first side surface 317b and the bottom surface 317a are connected with a rounded corner with a radius of R1, and the second side surface 317c and the bottom surface 317a are connected with a rounded corner with a radius of R2, and the radius R1<radius R2 (Figure 4). In this embodiment, R1 = 3.0 mm and R2 = 0.5 mm, but they are not limited thereto, and can be appropriately set to a size that can suppress stress concentration.

When pre-bending the unbent ground electrode 40A, as shown in FIG. 6 , a load is applied to the contact surface 319 of the second member 311B of the bending spacer 311 to bend the unbent ground electrode 40A by the bending roller 331 . When stress is concentrated on the portion of the second member 311B where the groove portion 317 is formed due to the load by the roller 331 , breakage (cracks) is likely to occur at the stress-concentrated portion. In the present embodiment, by making the radius R2 of the rounded corner of the joint between the second side surface 317c and the bottom surface 317a to which a relatively high stress is applied in the groove portion 317 larger, the concentration of stress can be suppressed, thereby enabling Breakage of the second member 311B is suppressed.

FIG. 7 is an explanatory diagram for explaining the main bending process (step S184). The final bending device 250 includes a final bending punch 251 that can be driven in the vertical direction (Z-axis direction). In step S184 ( FIG. 2 ), the main bending punch 251 is brought into contact with the ground electrode 40 after the pre-bending process from above, and the main bending process is performed on the ground electrode 40 after the pre-bending process to make the tip of the ground electrode 40 The inner side surface 412 is parallel to the top surface 12 of the center electrode 10 . In the main bending process, the bending process is performed step by step while monitoring the distance between the electrode tip 45 and the tip surface of the center electrode 10 with the CCD camera 253 to form a spark discharge gap G of a predetermined size. In this way, spark plug 100 is completed.

Steps S10 to S18 described above are repeatedly implemented to continuously manufacture a plurality of spark plugs 100 . When the second member 311B of the bent spacer 311 is damaged during the continuous manufacture of a plurality of spark plugs, the second member 311B is replaced before step S18. When the first member 311A is damaged, similarly, the process of replacing the first member 311A is performed before step S18.

As described above, in the pre-bending step of bending the unbent ground electrode 40A of the spark plug 100, since the bending load acts on the spacer 311, there is a possibility that the bending load may be placed on the mounting portion (first The member 311A) or the groove portion 317 of the second member 311B is damaged. According to the spark plug manufacturing method of the present embodiment, in the pre-bending step, the bending spacer 311 configured to be divisible into two members (first member 311A, second member 311B) is used. Therefore, when any one of the first member 311A and the second member 311B is damaged, it is only necessary to replace the damaged member. Compared with the case where the entire pad 311 is replaced, it is possible to prevent the tooling from being damaged. (Japanese: Jig tool) replacement cost, so that the manufacturing cost of the spark plug 100 can be reduced. Also, for example, if the second member 311B is damaged (cracked), the accuracy of the spark discharge gap of the spark plug 100 may decrease. However, by replacing the second member 311B, the spark discharge gap can be stably and accurately formed.

In addition, the first member 311A and the second member 311B of the spacer 311 used in the manufacturing method of the spark plug of this embodiment have a so-called mating structure. Therefore, when replacing one of the first member 311A and the second member 311B, by fitting the convex portion 322B of the second member 311B into the concave portion 322A of the first member 311A, the first member 311A and the second member 311B can be easily replaced. The second member 311B is properly combined. Therefore, according to the manufacturing method of the spark plug of the present embodiment, when the first member 311A or the second member 311B of the bent spacer 311 is damaged, the member can be replaced appropriately in a short time, so the manufacturing time of the spark plug can be reduced. increase, thereby suppressing a decrease in productivity.

For the spacer 311 used in the manufacturing method of the spark plug of this embodiment, the first member 311A and the second member 311B are made of different steel materials, the toughness of the first member 311A is higher than that of the second member 311B, and the second member 311B is tougher than the second member 311B. The hardness of the member 311B is higher than that of the first member 311A. Since a large load is applied to the bending spacer 311 by the roller 331, the bending spacer 311 needs to have a large hardness that does not cause damage (crack) due to the load. The ground electrode 40 of the spark plug 100 according to the present embodiment is shorter than conventional ones (structures in which the tip 45 does not protrude from the tip of the ground electrode 40 , and a structure without the tip 45 ). When the pre-bending process is performed, the load (stress) acting on the spacer 311 is larger than before, and the possibility of damage to the bent spacer 311 increases. Therefore, increasing the overall hardness of the flex pad 311 has been studied, but if the overall hardness is increased, the possibility of damage to the portion of the flex pad 311 attached to the flex pad positioning mechanism 310 increases. Therefore, the curved spacer 311 is configured to be divisible, the first member 311A is a member with high hardness and high toughness, and the second member 311B is tougher than the first member 311A but has a toughness. A member having a hardness higher than that of the first member 311A. Thus, the curved spacer 311 becomes a balanced jig, which is less likely to be damaged. Therefore, the replacement cost of the jig can be reduced, and the manufacturing cost of the spark plug can be reduced.

For the spacer 311 used in the method of manufacturing the spark plug of the present embodiment, the angle R of the portion where the stress due to the load generated by the bending roller 331 concentrates in the groove portion 317 of the second member 311B is set. is larger, the concentration of stress can be suppressed, and damage to the second member 311B can be suppressed. As a result, the cost and time required for replacing the members of the bent spacer 311 in the manufacturing process of the spark plug can be suppressed, thereby suppressing the manufacturing cost of the spark plug and suppressing a decrease in production efficiency.

B. Variations:

The present invention is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the gist thereof. For example, in order to solve part or all of the above-mentioned problems, or to achieve part or all of the above-mentioned effects, the technical features in the embodiments corresponding to the technical features in each technical solution described in the column of the content of the invention can be appropriately exchanged, combination. In addition, if the technical feature is not described as an essential content in this specification, it can be deleted appropriately. For example, deformations such as the following are also possible.

B-1. The first modified example:

In the above embodiment, the structure in which the electrode tip 45 is joined to the tip of the ground electrode 40 in a state protruding from the tip surface of the ground electrode 40 was exemplified, but the present invention is not limited thereto. For example, the electrode tip 45 may be joined at a position inside (on the −Y axis side) of the tip surface of the ground electrode 40 . In this case, the ground electrode 40 is formed longer than in the above-described embodiment. In addition, the structure which does not have the electrode tip 45 may be sufficient.

B-2. Second modified example:

In the above embodiment, an example in which the bending spacer 311 is divisible into two members (the first member 311A and the second member 311B) was shown, but it may be configured into three or more members. By making the bending spacer 311 divisible, in the event of damage or the like, only the member including the damaged part can be replaced, thereby reducing the replacement cost of the jig.

B-3. The third modified example:

The shape of the curved spacer 311 is not limited to the above embodiment. The curved spacer 311 only needs to include an attachment portion capable of being attached to the curved spacer positioning mechanism 310 and a contact surface 319 having a curved shape corresponding to the curved shape of the ground electrode 40 . The position where the bending spacer 311 is divided is not limited to the above-mentioned embodiment, but can be set appropriately.

B-4. Fourth modified example:

The shape of the recessed part 322A and the convex part 322B respectively formed in the 1st member 311A and the 2nd member 311B is not limited to the said embodiment. The recessed part 322A and the convex part 322B should just be the shape which can fit mutually. For example, the first member 311A may have a convex portion, and the second member 311B may have a corresponding concave portion.

B-5. Fifth modified example:

The material constituting the first member 311A and the second member 311B is not limited to the above-mentioned embodiment. For example, the second member 311B may be formed using the same alloy tool steel SKS3 as that of the first member 311A. Even if the first member 311A and the second member 311B are made of the same material, if any one of the first member 311A and the second member 311B is damaged, only the damaged member can be replaced. The cost of jig replacement can be reduced. In addition, a part of the second member 311B that is in contact with the unbent ground electrode 40A may be formed using a material with higher hardness (for example, cemented carbide V2 or the like).

B-6. The sixth modified example:

In the above-mentioned embodiment, an example was shown in which the fillet radius of the connecting portion between the bottom surface and the side surface of the groove portion 317 was set to a different value at the first side surface and the second side surface, but it is not limited thereto, and may be Set to the same corner radius.

Explanation of reference signs

10. Center electrode; 12. Top surface; 19. Terminal metal piece; 20. Insulator; 29. Shaft hole; 30. Main metal shell; 31. End face; 40. Grounding electrode; 40A, unbent grounding electrode; 45. Electrode head; 50, main body metal shell; 90, internal combustion engine; 91, inner wall; 92, combustion chamber; 100, spark plug; 150, workpiece; 250, formal bending device; 251, punch; 253, CCD camera; 300, pre- Bending device; 310, positioning mechanism part of bending pad; 311, bending pad; 311A, first component; 311B, second component; 312, bolt; , groove portion; 317a, bottom surface; 317b, first side surface; 317c, second side surface; 317d, third side surface; 318, concave portion; 319, contact surface; 321, through hole; 322A, concave portion; 330, bending mechanism part; 331, roller; 412, inner side; CA, axis.

Claims (5)

1. a kind of manufacture method of spark plug, the spark plug include：Central electrode, it extends in the axial direction；Base metal shell Body, it is located at the periphery of the central electrode；And grounding electrode, to be bar-shaped, the cardinal extremity of the grounding electrode is engaged in described for it Base metal housing, and the top of the grounding electrode is to axis lateral bend, wherein,

The manufacture method of the spark plug includes bending operation, in the bending operation, by by the unbent grounding electrode Do not bend grounding electrode and press on defined curved surface possessed by bending cushion block, so that grounding electrode bending is not bent,

The bending cushion block is configured to be divided into more than two components including the 1st component and the 2nd component, and this 1 component, which has, to be used to the bending cushion block being installed on the installation portion of fixed jig, the 2nd component have be used for it is described not curved The defined curved surface that bent grounding electrode is in contact.

2. the manufacture method of spark plug according to claim 1, wherein,

Form it is described bending cushion block it is described two more than component among, at least two components, one Component with convex portion and another component with can be mutually chimeric with the convex portion recess.

3. the manufacture method of spark plug according to claim 1 or 2, wherein,

In the bending cushion block, the toughness of the 1st component is higher than the toughness of the 2nd component, the hardness of the 2nd component Higher than the hardness of the 1st component.

4. the manufacture method of spark plug according to any one of claim 1 to 3, wherein,

The grounding electrode of the spark plug also includes electrode tip, the electrode tip be engaged in the top and be configured as with The mode in gap is relative with the central electrode as defined in having between the electrode tip and the central electrode,

The bending cushion block is for having and can hold with the defined curved surface for not bending grounding electrode and being in contact Receive the groove portion of the electrode tip,

The groove portion includes the 1st side, bottom surface and the 2nd side, and the 1st side is configured at the described 2nd of the bending cushion block The tip side of component, the bottom surface and the 1st side are mutually continuous, the 2nd side it is relative with the 1st side and with the bottom surface It is mutually continuous,

Between 1st side and the bottom surface by with radius for R1 fillet in a manner of be connected, the 2nd side and institute State between bottom surface by with radius for R2 fillet in a manner of be connected, radius R2 described in the radius R1 ＜.

5. the manufacture method of spark plug according to any one of claim 1 to 4, wherein,

In the case that any component of the manufacture method of the spark plug in the component of the bending cushion block generates breakage, There is the process for the component for changing the breakage before the bending operation.